Plasma Homocysteine in Obese, Overweight and Normal Weight
Hypertensives and Normotensives.
Rubina A Karatela, Gurmukh S. Sainani
Jaslok Hospital And Research Centre, 15, Dr. G. Deshmukh Marg, Mumbai:26

metabolic diseases such as coronary heart disease (CAD), hypertension, and dyslipidemia. Obesity is a leading risk factor for chronic arterial hypertension12. Moreover, obesity significantly increases the risk for the occurrence of cardiovascular disease (CVD) in patients with essential hypertension. Obese men have higher risk for increased arterial pressure values. No prior study has examined the relation of plasma homocysteine to hypertension in obese and overweight Indian subjects. Thus, the aim of the present study was to assess the interrelationship of obesity with plasma homocysteine levels as well as vitamin B12 and folic acid levels and dyslipdemia in hypertensive and normotensive subjects.
MATERIALS AND METHODS
Subjects selection
Trained interviewers and physicians took measurements using a mercury sphygmomanometer according to standardized BP measurement protocols recommended. The average of all available measurements was used in this study. A person was considered to have hypertension if blood pressure met the

Correspondence: Dr.G.S Sainani, Sainani Medicare Clinic, 401,Doctor House, Pedder road, Mumbai:26
E-mail: drsainani@vsnl.com

definition of stage I hypertension: elevated systolic BP (>140 mmHg), elevated DBP (> 90 mmHg) (Joint National Committee, JNC 7 criteria). Sixty-five hypertensive patients were undertaken for the present study. These patients had not started taking medications for hypertension. Exclusions included recent myocardial infraction (MI), stroke with residual paresis, uncontrolled congestive heart failure (CHF), peripheral arterial disease with evidence of tissue injury or loss, and established deficiency of vitamin B12 or folate. Also, sixty-five normotensive subjects were selected. These had normal BP (<120/80), and no history of hypertension, diabetes mellitus (type 2), or any vascular disease and with no established deficiency of vitamin B12 or folate, with normal ECG, normal chest X-ray, normal blood glucose and negative stress test. Informed consent was obtained from each study participant. The present study was approved by the Ethics Committee of Jaslok Hospital and Research Centre. Body mass index (BMI-weight in kg/height in m2) was used as a measure of overall obesity. Overweight subjects were defined as those with BMI 25-29.9 kg/m2, while obese as those with >30kg/m2.
Analytical method
Fasting venous blood sample of all the study participants was drawn at morning after a 12-hour fast for estimations of various biochemical and haematological parameters. Plasma total fasting homocysteine which refers to the sum of protein-bound, freeoxidized and reduced species of homocysteine in plasma was determined by enzyme immunoassay (Axis® Shield, AS, Norway). Serum levels of vitamin B12 and folic acid levels were
determined by radioimmunoassay [Diasorin ® SimullTRACSNB Radioimmuassay kit vitamin B12 (57Co)/ Folate (125I)]. Blood lipids ie. total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), very low-density lipoprotein cholesterol (VLDL), lipoprotein-a (Lpa) and triglycerides were analyzed spectrophotometrically using on Cobus Integra ® autoanalyzer (Roche® Diagnostics). A comprehensive Lipid Tetrad Index (LTI) was determined to reflect the total burden of dyslipidemia11. It was derived by multiplying the three lipids directly associated with CAD and dividing the product by HDL, which is inversely associated [total cholesterol x triglycerides x Lp(a)/ HDL].Pulse pressure was determined as: SBP – DBP; whereas mean arterial pressure was evaluated as: SBP/3 + 2DBP/3
Statistical analysis
Results were expressed as mean ± standard error of mean. Simple correlations by the Pearson’s method allowed us to assess the univariate relations. Statistical analysis was performed using the Statistical Package ie. SPSS-PC.(version 10. SPSS, Inc.,Chicago, IL). Differences and correlations were considered significant at p-valve< 0.05.

RESULTS
Among the hypertensive subjects, 31.9% were normal weight, 50.7% were overweight and 17.4% were obese; whereas, among the normotensives subjects, 49.2% had normal weight, 35.4% were overweight and 15.4% were obese. We observed high prevalence of hyperhomocysteinemia (38.5%) and dyslipidemia ie. LTI> 20,000 (33.9%) along with reduced levels of vitamin B12 and folic acid (52.3%), among the hypertensives when compared to the normotensives which had comparatively lower prevalence of hyperhomocysteinemia (10.77%), dyslipidemia (8.1%) and reduced vitamin levels (3.2%). Among the hypertensives, out of the total hyperhomocysteinemic,70.6% had reduced vitamin levels; whereas, among the normotensives, out of total hyperhomocyteinemic, 5% had reduced vitamin levels.

Table 1. Characteristics of hypertensive patients

Table 1 shows the various characteristics of the hypertensive subjects which were divided into sub-group I ie. normal weight and sub-group II ie. obese and overweight subjects. Among the overweight and obese hypertensives, we observed significantly raised plasma homocysteine, reduced vitamin B12 and folic acid levels, raised blood pressure levels (systolic and diastolic), pulse pressure, dyslipidemia compared to normal weight hypertensives. Table 2 shows the various characteristics of the normotensive subjects which were divided into sub-group III ie. normal weight

Table 2 . Characteristics of normotensive subjects

and sub-group IV ie. obese and overweight subjects. Among the overweight and obese normotensives, we observed significantly raised plasma homocysteine, reduced vitamin B12 and folic acid levels compared to normal weight normotensives. Also the BP levels were in higher normal range in obese and overweight normotensives compared to normal weight normotensives. On comparison between the normal weight sub-groups I and III ie. of hypertensive and normotensive subjects, we observed raised homocysteine (p<0.04), dyslipidemia (p<0.03), raised SBP & DBP, pulse pressure levels (all p<0.0001), along with reduced levels of vitamin B12 and folic acid (p<0.0004) among the former sub-group ie. normal weight hypertensive compared to the normal weight normotensive subjects. Also, on comparison between the obese and overweight subgroups II and IV ie. of hypertensive and normotensive subjects, we observed similar results ie. raised homocysteine (p<0.001), dyslipidemia (p<0.04), raised blood pressure (systolic and diastolic), pulse pressure levels (all p<0.0001), along with reduced levels of vitamin B12 and folic acid (p<0.0001) among the subgroup of obese and overweight hypertensives compared to the subgroup of obese and overweight normotensives. On performing correlation analysis [Table 3] in hypertensive subjects, we observed plasma homocysteine positively correlated significantly with BMI and arterial pressure levels, and negatively with vitamin B12, folic acid levels. And among the normotensive subjects, homocysteine was correlated mildly significantly with BMI and negatively with vitamin B12 and folic acid levels.

Table 3: Correlation Analysis of plasma homocysteine

r: Pearson’s coefficient

DISCUSSION Among the obese and overweight hypertensives, we observed significantly raised plasma homocysteine, reduced vitamin B12 and folic acid levels, raised BP (SBP & DBP), pulse pressure and severe dyslipidemia compared to normal weight hypertensives. Also, among the obese and overweight normotensives, we observed significantly raised plasma homocysteine and reduced vitamin B12 and folic acid level compared to normal weight normotensives. The blood pressure

levels were in higher normal range in obese and overweight normotensives compared to normal weight normotensives. As the BMI of the hypertensives increased, the plasma levels of homocysteine and the arterial pressure levels also raised, along with a reduction in vitamin levels. Weight gain is associated with a high risk of developing cardiovascular and metabolic diseases such as CAD, hypertension, and dyslipidemia. Obesity is a leading risk factor for chronic arterial hypertension12. Epidemiological studies have documented a close relationship between BMI and cardiovascular events13-14. The association between body weight and blood pressure has been found even in normotensive subjects with normal BMI15. Subsequently, clinical studies have demonstrated that weight loss reduces arterial pressure and corrects diabetes and other comorbidities associated with obesity16. Although the association of obesity and hypertension is well recognized, the mechanisms involved in the pathogenesis of increased BP in the obese are poorly understood, and most likely represents the interaction of demographic, genetic, hormonal, renal, and hemodynamic factors 15 . The mechanisms that may lead to hypertension in obese individuals include increased SNS activity, insulin resistance and hyperinsulinemia, sodium retention, and enhanced vascular reactivity. These abnormalities are interrelated in a complex fashion. Clinically, hypertensive obese subjects are more likely to develop left ventricular hypertrophy and kidney damage than their lean counterparts17. Hence, to evaluate if homocysteine was interrelated to obesity and hypertension, we performed the present study, since the vascular risk associated with hyperhomocysteinemia has been observed to be stronger in hypertensive individuals. Mechanisms that could explain the relationship between homocysteine and blood pressure include homocysteine-induced arteriolar constriction, renal dysfunction and increased sodium reabsorption
and increased arterial stiffness. Hyperhomocysteinemia enhances arterial stiffness leading to an increase in pulse pressure, mainly due to elevated systolic blood pressure, and in cardiac load. High homocysteine concentrations are also associated with endothelial cytotoxicity and impaired endothelial function18. Furthermore, homocysteine may increase insulin resistance, which leads to a higher blood pressure. In the third National Health and Nutrition Examination Survey (NHANES III), persons in the highest quintile of plasma homocysteine had a 2- to 3-fold increased prevalence of hypertension relative to those in the lowest quintile19. A considerable body of evidence suggests a role for plasma homocysteine in the pathogenesis of hypertension6. Some studies did not3 and some did find a significant, although weak, association between plasma homocysteine and blood pressure2,9,10. Obesity significantly increases the risk for the occurrence of